Question

# If the mean of five observations x, x + 2, x + 4, x + 6 and x + 8 is 11, then the value of x is (a) 5 (b) 6 (c) 7 (d) 8

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Solution

## (c) 7 Mean of 5 observations = 11 We know: $\mathrm{Mean}=\frac{\mathrm{Sum}\mathrm{of}\mathrm{all}\mathrm{observations}}{\mathrm{Total}\mathrm{number}\mathrm{of}\mathrm{observations}}\phantom{\rule{0ex}{0ex}}⇒11=\frac{x+x+2+x+4+x+6+x+8}{5}\phantom{\rule{0ex}{0ex}}⇒11=\frac{5x+20}{5}\phantom{\rule{0ex}{0ex}}⇒5x+20=55\phantom{\rule{0ex}{0ex}}⇒5x=35\phantom{\rule{0ex}{0ex}}⇒x=7$

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